1. Field of the Invention
This invention relates to an apparatus for feeding, in fluid form, a compound or composition source which is susceptible to contamination, decomposition or denaturation on contact with the outer environment such as the atmosphere or light. More particularly, it relates to a raw material feeding apparatus capable of protecting the raw material against influences of the outer environment through cleaning and drying operations.
2. Description of the Related Art
Raw materials used in chemical vapor deposition (CVD) or atomic layer deposition (ALD) processes, which are called precursors, are reactive with water, oxygen, carbon dioxide or light, including silicon compounds, phosphorus compounds, boron compounds, metal compounds, and mixtures thereof. Such a raw material easily produces a solid phase deposit in pipes and valves on contact with the outer environment when the container of the raw material is attached or detached. The solid phase deposit influences vapor delivery and vapor phase growth reaction or adversely affects semiconductor thin film quality. A solid phase deposit of highly reactive materials such as alkyl metal compounds can ignite or explode. In analysis processes, such as liquid chromatography and gas chromatography, if a substance under analysis undergoes the outer environmental influences markedly, accurate analysis is not expected.
In the above-exemplified processes for production or analysis dealing with a fluid form source susceptible to contamination, decomposition or denaturation on contact with the outer environment, it has been demanded to establish a method of preventing the source from generating a decomposition or reaction product harmful to the process or a method of completely removing the decomposition or reaction product.
To address the problem, the following techniques have been proposed. JP-A-2001-108199 discloses a method in which a container for raw material delivery is used with a piping and valving configuration designed to enable purging any raw material remaining in the system with a fluid. JP-A-6-244120 also proposes a raw material feed system with a piping and valving configuration designed to enable purging and evacuation of the system. JP-A-2002-343719 discloses a feed system comprising a raw material container, a cleaning fluid container, and a container for a used cleaning fluid, the piping of which is easily purged and evacuated. These related techniques, however, do not bring about satisfactory solutions to the outstanding problem.